Thermostatic control of furnaces.



J. H. ROBERTS.

THERMOSTATIC CONTROL OF FURNACES.

APPLICATION r1150 APR.12. 1913.

1,15%,207. Patented Sept. 21, 1915.

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J'. H. ROBERTS.

THERMOSTATIC CONTROL OF FURNACES.

APPLICATION FILED APR. 12. \9l3.

PatentedSept. 21, 1915.

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THERMOSTATIG CONTROL OF FURNACES.

Specification of Letters Patent.

Patented Sept. 21, 1915.

Application filed April 12, 1913. Serial No. 760,677.

To all whom itmay concern:

Be it known that I, JOHN HENRY Ron- ERTS, a citizen of the UnitedStates, residing at Chicago, in the county of Cook and State ofIllinois, have invented certain new and useful Improvements inThermostatic Control of Furnaces, of which the following is aspecification.

This invention relates to the thermostatic control of furnaces, withparticular appli-' cation to that class of combined furnaces and driersin which the products of combus tion from the furnace are caused to flowin physical contact with the material to be dried.

A" primary object of the invention, as applied .to devices of the'abovetype, is to provide a method and means for automatically regulating thevolume of gas flowing over or through the material, while maintaining apractically constant temperature in the entering gases. This result Iaccomplish by a thermostatic regulation of the fuel-supply and of theair for fuel-combustion, in conjunction with a simultaneous regulationof air admitted to the gas-stream at a point or points beyond thecombustion zone, and between the combustion zone and the thermostat. Inthis manner, the variations in the quantity of air supplied for thecombustion of the fuel may be compensated to any desired degree bycorresponding variations in the'quantity of air supplied for admixturewith the gases of combustion, in such manner as to regulate and controlthe total volume of gases, and the velocity of the gas-stream. Thisregulation is of the highest technical importance in all cases in whichthe evaporation of moisture is. required to proceed, at a uniform rate,or in which the velocity of the gas-stream must be regulated withreference to its capability of blowing the dried or partially driedmaterial from the apparatus.

For a full understanding of my invention, it will be described byreference to a preferred embodiment thereof, as shown in theaccompanying drawings, it being understood that the invention is notrestricted in its application to the particular type of furnace or drierchosen for illustration.

In said drawingsFigure 1 is a side elevation of a typical furnace anddrier, the central portion being broken away, showing the applicationthereto of the thermostatic regulator embodying my invention; Fig. 2shows one end of the apparatus of Fig. 1, viewed from above, thefeed-hopper being removed; and Fig. 3 is a vertical section on lineIII-III of Fig. 1.

1 represents an inclined cylindrical drier which may be of any preferredconstruction, mounted for rotation upon rollers 2, 2, and driven by abevel-gear 3 operating a pinion 4: which engages the circular rack 5.The

cylinder is inclosed by the usual masonry walls 6, and under its forwardend is a mechanically-operated furnace 7, which may be of any desiredcharacter or construction, and adapted for the consumption of coal, oilor other fuel.

The drawings illustrate a coal furnace having grate bars 8, a cokingretort 9, and a steam-operated mechanical stoker 10. The combustiongases from the furnace flow beneath and around the drying cylinder 1,and thence through the same, and are withdrawn laterally by the suctionfan 11, the general path of the gases being as indicated by the arrowson Fig. 1. The material to be dried, as for example a vegetable prodnot, is introduced into the hopper 12, passes through the cylinder 1 ina direction opposite to the gas-flow, and is discharged into themechanical conveyer 13.

14 is a pressure blower for supplying air beneath the grate 8, and 15 isa steam engine coupled directly to the blower.

The foregoing elements may be of any standard or desired construction.

16 represents an air-compressor, 17 an airreceiving tank, and 18 athermostatically controlled air-valve in the discharge line 19 from theair-tank 17. The thermostat 20, controlling the valve 18, is located inthe path of the combustion gases, and may be of any approvedconstruction, serving merely to open the valve 18 when a definitetemperature of the gas is exceeded.

21 represents an air-conduit extending between the air-valve 18 and adiaphragmvalve 22.

23 is a steam-line, having a branch line 24L leading to the cylinder ofthe blower engine 15, the passage of steam through this branch line 24being controlled in known manner by the diaphragm-valve 22.

25, 25 are diaphragm-motors connected respectively to a pair of dampers26, 26 located on opposite sides of the furnace cas 'ing, and servingwhen open to admit air to the flues 27 for admixture with the combuslingthe reciprocation of the stoker piston and the rate of feed of fuel fromthe hopper 36. The reversing valve 31 is operated by a belt 37 from theblower engine 15, so that the diaphragm-valve 22 controls simultaneouslyand proportionately the rate of supply of fuel by the stoker, and theair-supply for fuel-combustion by the blower 14.

Constant air-pressure in the tan 17 is maintained by providing adiaphragm-valve 38, governing the steam-supply to the aircompressor 16,and controlledby the airpressure in tank 17, through a pipeconnection39.

The construction ofthe several'individual elements above mentioned,viz.,' the thermostat 20 and the air-valve 18 controlled thereby, andthe controllingdevices 22 and 25, forms no part of the presentinvention, and all of said elements may be of any standard or approvedtype. I

The mode of operation of the above-described controlling apparatus is asfollows: The thermostatic valve 18 is so adjusted that it will remainclosed at the gas-temperature which it is desired tomaintain, but willopen in case such, temperature. is exceeded.

So long as such temperature is not exceeded,

the fuel and the air for fuel combustion will be supplied at the normalrate, and the dam pers 26 will either remain closed, or they may be setin a partially open position to supply-the desired amount of auxiliaryair to maintain the proper normal volume and velocity of air-flow. Thecapacity of the furnace and stoker should of course be suflicientreadily to maintain the desired temperature.

In case the temperature of the gas exceeds the desired degree,thethermostatic valve 18,

off or reduce the steam-supply to the engine 15, with the result that alesser quantity of air is supplied for combustion: at the same desiredstandard, whereupon the thermo-' static valve 18 again closes, and thefuel and air for combustion purposes are again supplied at the normalrate. In this manner the temperature of the gases is controlled withgreat accuracy.

A temperature-control simply as above described would involve afluctuation of the volume of the gas traversing the drier, inasmuch asthe control of the temperature is effected by varying the amount of airsupplied for combustion and such fluctuation is in practice highlyobjectionable, for the reason that it involves a correspondingfluctuation in the evaporative capacity of the gases, and hence in themoisture-content of thematerial to be dried, assuming the latter to passthrough the apparatus ata uniform rate. According to my invention, suchfluctuation is overcome by the provision of the air-dampers 26,controlled by the diaphragm-motors 25. Admission of air to thediaphragm-motors 25 causes these to actuate the levers 40, with theirconnecting links 41, and thereby to open the dampers 26, through whichair is drawn under the constant draft of the suction fan 11. Byadjusting the position of the links 41, the de gree to which the dampers26 are opened may be so controlled as to compensate with any degree ofaccuracyfor the reduced supply of air from the blower 14, therebyavoiding or minimizing the fluctuations in the volume and velocity ofthe gases. It will thus be seen that the invention provides for theautomatic regulation of the temperature of the gas-stream, withoutvarying the volume v or velocity of the gas, or with such cor 701 of thevolume and velocity of'the gas-stream as may be practically necessaryunder the circumstances arising inthe treatment of any particularmaterial.

I claim 1. The herein-described method of regu I lating the volume of acurrent of gases of combustion under substantially constanttemperature-conditions, which consists in thermostatically regulatingthe fuel-Suppl and the air for fuel-combustion "in accord ance with'thetemperature of, the gas-current, and effecting a simultaneous adjustmentof the volume of the'ga's-current by controlling the admission of airthereto beyond the combustion zone.

2. Apparatus for regulating the volume of a current of gases ofcombustion under substantially constant temperature-conditions,comprising means for thermostatic regulation of the fuel-supply and theair for fuel- In testimony whereof I affix my signature combustion inaccordance with the temperain presence of two Witnesses.

ture of the gas-current, in combination with JOHN HENRY ROBERTS. meansfor simultaneously controlling the ad- Witnesses:

mission of air to said gas-current beyond the MABEL HAsELTINE,

combustion zone. L. W. BROCKETT.

